calibration and validation swmm model in order to simulate urban runoff (case study: imam ali town in mashhad)

large impervious surfaces and man-made waterways are the characteristic of urban area. increasing urbanization and rapid growth of cities in recent decades towards the upstream watershed, has been severely affected on rainfall-runoff processes in urban area. therefore, to computer models in order to illustrate these processes the proper design or assessment of urban drainage systems has special attention. the purpose of this study is simulation and validation the volume of runoff and calibrated swmm model in small urban area. required parameters of the model using land use maps, dem of study area, and field inspection were calculated. for calibration and validation process model, corresponding to three event rainfall runoff measured at the output of the basin and was compared with runoff simulated by the model. the results showed there is good agreement between simulated and observed runoff discharge and depth. there is a little difference between simulated and observed for runoff rate but this difference is more than acceptable value (ns>0.5). ns value for the first, second and third event is the, 0.69, 0.85 and 0.52 respectively. this performance represents that the swmm model is effective in the study area and this model can be used for in appropriate designs, and evaluate network systems in urban drainage.